An electron capture detector is employed as a detector for a gas chromatograph. As a detection principle of this electron capture detector, a method using radiation and a method without using radiation are known.
As the electron capture detector without using the radiation, there are known those described in Patent Documents 1 and 2. The electron capture detector described in the Patent Document 1 generates a discharge in He and uses deep-UV rays when He2 returns to a ground state, for generation of plasma (positive ions and electrons).
Furthermore, the electron capture detector described in the Patent Document 2 performs ionization by deep-UV rays generated from a deep-UV lamp.
Because such an electron capture detector does not generate radial rays, the electron capture detector is easy to handle and convenient for outdoor measurement of groundwater, soil gas or the like.
There is known a nonradiative electron capture detector using a discharge phenomenon in rare gas (described in, for example, the Patent Document 1).
As a nonradiative electron capture detector of this type, a photoionized electron capture detector by a pulsed discharge (pulsed-discharge photoionized electron capture detector) as shown in FIG. 8 is known, for example.
With this method, the pulsed discharge causes transition of helium to an excited state (Formula (1)), dopant gas is ionized by UV-rays (Formula (2)) generated when helium in the excited state returns to the ground state (Formula (3)), and the quantity of generated free electrons is measured as the ground current in the detector.
This ground current is a current value when detection target component does not exist in the detector. If an electron-affinic detection target component (M) flows into the detector through a column, an electron capture reaction of the detection target component occurs to decrease the quantity of free electrons in the detector (Formula (4)), with the result that the ground current lowers. A response principle of the detector that such a change in ground current is grasped as a chromatogram is exactly identical to that of a radiative electron capture detector.He→He*  Formula (1)He*→He+hv  Formula (2)Xe→Xe++e−  Formula (3)M+c−→M−  Formula (4)
Patent Document 1: Japanese Patent Application National Publication Laid-Open No. 9-507573
Patent Document 2: Japanese Patent Application Laid-Open No. 4-303759